Autoimmune responses involving renal basement membrane antigens and other renal cellular antigenic constituents are involved in a significant proportion of nephritogenic immune responses leading to development of glomerulonephritis and tubulointerstitial nephritis. Almost nothing is known about the physiology or metabolism of these renal basement membrane antigens or antigens derived from renal cells, or the events that lead to the autoimmune responses to them. Radioimmunoassays are being developed to quantitate these materials so that their normal physiologic levels in the body fluids can be established. The effects of potentially immunogenic events on the physiology and antigenicity of these materials can then be determined. The radioimmune assays can be used in turn to further isolate and purify the nephritogenic antigens for further study. In order to extend our knowledge of the introduction of nephritis, it is essential to understand the events responsible for the initiation of immune responses to renal constituents involved in the immunopathogenesis of both glomerulonephritis and tubular interstitial nephritis.